The present invention relates to a process for depositing a metal-oxide-based layer on a glass substrate. It also relates to the glass substrate according to this process and to its applications.
It is well known in the prior art to use techniques called "pyrolysis" to coat a glass substrate with one or more thin layers, and to do so for the purpose of conferring particular properties on it, especially electrical properties, thermal properties, mechanical properties, etc.
These techniques consist in spraying "precursors", for example of an organometallic type, in gas form or in powder form or in liquid form, by themselves or in solution in a liquid, onto the surface of the substrate which is heated to a high temperature.
The said precursors, upon contact with the substrate, decompose thereon, leaving, for example, a metal, oxide, oxynitride or nitride layer. The advantage of pyrolysis is well understood: it resides in the fact that it allows layers to be deposited directly on the ribbon of glass in a line for manufacturing flat glass of the float type, in a continuous manner, and also in the fact that the deposited layers adhere strongly to the substrate.
Among these layers, it has been known for a very long time that tin-oxide-based layers are particularly advantageous since their properties, especially electrical and optical properties, make the coated glass substrates useful for a good number of applications.
Many tin precursors have already been tested successfully in the past, particularly those which can be vaporized at the surface of the hot glass using one of the aforementioned techniques, called CVD (Chemical Vapour Deposition).
In order to improve the electrical properties of these tin-oxide based layers mentioned above, attempts have been made to incorporate one or more dopants into the oxide. Several materials have been extensively tested in this regard, but the element which has provided most adaptable for tin oxide is fluorine.
Always with a concern to achieve doping efficacy, efforts have therefore been made to formulate, from a given tin precursor, a fluorine precursor which is the most appropriate for the tin precursor, more particularly when it is deposited by chemical vapour deposition (CVD).
To date, the many formulations that have been produced result in coatings consisting of layers of the aforementioned F:SnO.sub.2 type on glass substrates by chemical deposition that are generally satisfactory in terms of quality and with regard to the level of optical and/or electrical performance achieved.
However, whatever the chemical nature and physical form of each of the fluorine and tin precursors, no process for depositing layers formed on glass substrates using these precursors has achieved a high enough efficiency.
This is because in order for a defined F:SnO.sub.2 layer thickness to be obtained, a large amount of tin precursor is needed.